The harvest factor of a power station is the relationship between over the entire life span the won Nutz-Energie and that energy, which must be used for the production and installation of the work, and which are sometimes called also grey energy.

It is defined as the quotient of the energy produced during the actual working time and the energy which can be spent in the plant life cycle. Simply said, he gives answer to the question: "How often does one get the put in energy again Values over 1 mean a positive total energy balance.

Determination of the harvest factor

The harvest factor is differently computed by different groups of interests:

Generally for conventional (fossil) power stations also the assigned fuel was also included into the calculation, there these after (river) the production were irrevocablly burned. Thus fossil power stations have a factor smaller one, while renewable energies than only ones can have higher values, there of them "fuels" (wind, water, sun) after human discretion infinite are always and particularly by (lasting) use not to use itself.

Operators of conventional power stations however exclude the fuel gladly from the computation, and compare only the energy needed for the building and maintenance with the produced energy. So also they can reach a number more largely one.

The computation of the entire energy necessary for the production of a product is very and varies therefore depending upon source (and interest situation of the strongly, so that also the indicated harvest factors vary strongly.

Plants, which use more energy for their production, than they produce afterwards, contradict a lasting development

Values of the harvest factor

In this table the harvest factors indicated in some different sources are together calm:

Example calculation Fotovoltaikanlage

For the production, transport, maintenance etc. energy is needed - among other things in the form of electric current and one can compute heat these - for example on the basis the electricity bill of the involved factories, the fuel consumption of the trucks etc. If the plant is built, it produces Strom.Der harvest factor indicates now, how much more (electrical) produces energy the plant in the course of their life, as altogether energy for your production, structure and dismantling at the end of life is needed.

For a modern plant the factor is for instance about 7 (computation: Amortization period three years, life span at least 20 years).

Energetic amortization period

The energetic amortization period is connected closely with the term harvest factor. Admits is it also under the terms energy return time or simply only energetic amortization.

The energetic amortization period describes the time, over which an energy production plant must be operated, until the energy spent on the production again "produced" is. While plants, which are operated with renewable energies, can never reach energetic amortization periods of some months or years to have, conventional power stations according to this definition one point of the energetic amortization, since to the enterprise continuously further primary energy must be supplied. Therefore the indication of an energetic amortization is not meaningful with these power stations.

Energetic amortization period of wind energy plants

In the public discussion around the use of the wind energy the energetic amortization period of wind energy plants is often an issue between proponents ("only few months") and opponents ("no energetic amortization"). While first investigations from the pioneer time of the wind power utilization (1970er and early 1980er years) permitted, being based on unausgereiften test plants, quite the conclusion the fact that an energetic amortization is hardly possible occupies numerous studies since end of the 1980er years that the today's, matured standard equipment amortize in few months energetically.

With the results of the different investigations there are however certain differences. This is connected on the one hand with the strongly different, location-dependent energy yields of wind energy plants, on the other hand with the regarded life cycle. Besides often also the balance methods differ. Only the production of the plant is partly included regarded (old investigations), partly the energy expenditure for transport, maintenance over the lifetime and retreating longwall system with (newer investigations).

Examples

Energetic amortization periods of wind-powered devices:

Table energetic manufacture amortization periods

In the following energetic amortization periods (methodology become: without consideration of the fuel) mentioned, whereby energy expenditure for enterprise and outline are not considered against the actual definition of the harvest factor:

1) Pressurized water reactor, achievement 1,300 megawatts, direct dumping of used up Brennelemente2) achievement 1 megawatt, middle yearly wind velocity 4.5 - 5.5 m/s3) achievement 5 kilowatts (roof plant), polycrystalline and amorphous silicon.

Related links

• http://emsolar.ee.tu-berlin.de/allgemein/enamort.html
• http://www.volker-quaschning.de/datserv/kev/index.html

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